It has been proposed that the most common lipid abnormalities associated with the metabolic syndrome are elevated triglyceride and low high-density lipoprotein concentrations as well as the existence of small, dense low-density lipoprotein (LDL) particles. However, so far there are only limited clinical data concerning the distribution of LDL particles in patients with this syndrome. The aim of our study was to directly determine the concentration and relative distribution of LDL subfractions in patients with metabolic syndrome. One hundred seventy-five individuals were included. Patients with metabolic syndrome (n = 105) exhibited higher concentrations of dense LDL particles and lower mean LDL particle size than the control population (n = 70). Both of these parameters were significantly correlated with the number of components of metabolic syndrome. Multivariate analysis revealed that serum triglyceride concentration was the most important determinant of the presence of small, dense LDL particles. In conclusion, patients with metabolic syndrome exhibit higher concentrations of small, dense LDL subfractions than individuals who do not fulfill the criteria for the diagnosis of this syndrome. This increase is directly related to the number of components of metabolic syndrome and is mainly determined by the serum concentrations of triglycerides.